Establishing evidence of contact transfer in criminal investigation by a novel 'peptide coding' reagent

Forensic investigators are often faced with the challenge of forming a logical association between a suspect, object or location and a particular crime. This article documents the development of a novel reagent that may be used to establish evidence of physical contact between items and individuals as a result of criminal activity. Consisting of a fluorescent compound suspended within an oil-based medium, this reagent utilises the addition of short customisable peptide molecules of a specific known sequence as unique owner-registered 'codes'. This product may be applied onto goods or premises of criminal interest and subsequently transferred onto objects that contact target surfaces. Visualisation of the reagent is then achieved via fluorophore excitation, subsequently allowing rapid peptide recovery and analysis. Simple liquid-liquid extraction methods were devised to rapidly isolate the peptide from other reagent components prior to analysis by ESI-MS.